1. Field of the Invention
The following invention relates in general to hydraulic torque wrenches and more particularly to a safety activation device to prevent the wrench from activating before the wrench is in a safe position.
2. Description of the Prior Art
The petro-chemical industry, as well as industry in general, relies on extensive use of pipes and large valves with bolted or studded flanges. Very large make-up torque of the magnitude of 2,500-5,000 ft-lbs rising to as high as 75,000 ft-lbs are needed to tighten down the nuts on these flanges. Additionally, the break-out torque required may be four or five times the corresponding make-up torque needed for a given flange. Consequently, heavy-duty wrenches, primarily hydraulic torque wrenches, are needed. On such hydraulic torque wrench or power wrench is disclosed in U.S. Pat. No. 4,669,338 to Collins, which is incorporated by reference herein. FIG. 1 illustrates a power wrench such as disclosed in the '338 Patent wherein the ratcheting box wrench referred to generally as 1 is positioned on a flange-nut 2 in a manner so that the wrench body 3 will contact an adjacent flange-nut 4. Flange-nut 4 provides the reaction point or base from which the ratcheting box wrench 1 will gain leverage. Wrench 1 will have some type of actuation arm which rotates tool head assembly 8. In the embodiment shown, the activation arm comprises a piston and cylinder assembly. However, other activation arms such as power screws and the like may be utilized. The hydraulic cylinder 5 is activated and its piston rod (not shown) will extend causing the front cylinder clevis 6 to make contact with the lever arm 7 of the tool head assembly 8. The front cylinder clevis 6 is connected to the lever arm 7 with a connection pin 9. As the lever arm 7 is turned by the hydraulic cylinder 5, the tool read assembly 8 rotates. This rotation is further guided by a tracking arm 10 which is an integral part of the tool head assembly 8 located between the retainer arm 11 and the lever arm 7. The tracking arm 10 moves within an arcuate channel 12 (shown by hidden lines on FIG. 1) within the wrench body 3. If this tracking arm is properly dimensioned, it will increase the wrench's ability to operate within a confined space since there will be no need to remove and reattach the wrench to the nut during the exercise of a normal ratchet cycle.
It will be understood that when hydraulic fluid flows to cylinder 5 and clevis 6 extends in the direction of force arrow 13, body 3 will be urged in the direction of force arrow 14 against the reaction point, which is flange-nut 4 in FIG. 1. Torque is thereby applied to flange nut 2 in the direction indicated by force arrow 15. Typically, the wrench is activated by an activation switch 16, which is shown schematically in FIG. 1 as handheld remote 17 with activation button 45. While not shown in detail, it is known in the art to have a hydraulic fluid source 18 which will transmit hydraulic fluid to lines 9a or 9b on cylinder 5 in order to extend clevis 6 or retract it. It is similarly well know in the art how to activate transmission of fluid with a handheld remote 17. In other words, handheld remote is in operative connection with cylinder 5.
This configuration of wrench 1 operates safely as long as body 3 is placed against or very close to flange-nut 4 prior to activating wrench 1 (i.e., applying hydraulic pressure to cylinder 5). As may happen through inattentiveness, a worker may position wrench 1 on a flange-nut 2 as seen in FIG. 2. If the wrench is a ratchet type as disclosed in the above referenced U.S. Pat. No. 4,669,388, the ratcheting mechanism will allow the user to move body 3 against flange-nut 4. This is the proper manner of positioning wrench 1 before activating hydraulic cylinder 5. However, if body 3 is not placed safely against flange-nut 4 and if wrench 1 is activated while in this position, there is no reaction point to restrain the movement of body 3 and body 3 will move toward flange-nut 4 quickly and with great force. If a worker has placed his hand or fingers between flange-nut 4 and body 3, his hand or fingers may be seriously injured or even amputated. What is needed in the art is a wrench which insures body 3 is safely against a reaction point before fluid will flow to hydraulic cylinder 5.